Make App default to the generic consumer profile

[codeforester]

Summary

Make base_cli.App() use CliProfile.generic() when no profile is supplied.

Base already constructs and passes its explicit consumer profile, so this removes the last implicit Base behavior from the normal standalone entry point without changing Base's runtime contract.

Scope

• change the App default profile to the generic profile;
• keep CliProfile.legacy_base() available only as an explicitly named migration surface for the next extraction phase;
• update base-cli tests and documentation to make the default contract unambiguous;
• add regression coverage proving a default App() does not discover base_manifest.yaml, read ~/.base.d, or write Base-owned cache/history state.

Out of scope

• moving the legacy adapter implementation out of base-cli (follow-up phase of Remove remaining Base consumer coupling from base-cli #19);
• package rename;
• changes to Base, which already passes an explicit profile.

Acceptance criteria

• App() behaves like CliProfile.generic() by default.
• Existing Base consumers continue to pass and use their explicit profile unchanged.
• Documentation no longer describes the implicit legacy Base profile as the normal standalone behavior.
• Base-cli and Base consumer tests pass.